Facemasks or respirators are widely used to protect the user from inhaling dust or chemical particles, depending on the filter properties and certifications. The facemask comes in different sizes to suit the users of different facial geometry. For example, the mask sizes can be generalized as small, medium and large. For effective working of the mask, any gaps or loose fits of the mask on a human face should be avoided, when worn. The proper fit of the mask on the user face is obtained by selecting an appropriate size of the mask. To determine the appropriate size for a user, normally each size is tried on the user face and the appropriate size that suits the user face geometry is then determined. This is time consuming. To overcome this, many mask sizing gauges have been developed to easily determine the most appropriate size of the mask for a user.
WIPO Patent Application Number: WO 2013118034 discloses a sizing gauge that is structured to be used with a patient and is structured to enable an identification of a particular patient interface that is most appropriately sized for the patient. The sizing gauge includes a support portion and a sizing portion. The sizing portion includes a first gauge element and a plurality of second gauge elements. The first gauge element is disposed on the support portion and is structured to be positioned at a first location on the patient's face. The plurality of second gauge elements are disposed on the support portion and are situated at locations spaced from the first gauge element. The distance between the first gauge element and each second gauge element is representative of a size in one direction of each of at least some of the plurality of patient interfaces. At least one of the plurality of second gauge elements comprises a tactile feature.
U.S. Pat. No. 5,584,125 disclose a sizing guide for assisting in the initial determination of an appropriate size of respirator mask for a user thereof. The sizing guide has at least a first sizing gap having a known width such that comparison of the width of the first sizing gap with the length between a pair of facial landmarks such as the sellion landmark and the menton landmark provides an initial determination of the appropriate size respirator mask for the user which can then be fit tested. Preferably, the sizing guide also has a second sizing gap having a known width different from the width of the first sizing gap.
In above prior arts, the sizing gap or distance of the gauge element is compared with the length between a pair of facial landmarks. The gap or the measuring distance for each size in the gauge corresponds to at least one vertical distance at two points on each mask of various sizes. The sizes indicated on the gauge are obtained based on the dimensions of masks of various sizes.